In light of the numerous topics regarding joining different-diameter ropes via an EDK, I decided to pull-test a piece of 11mm static and 6mm cordelette joined by an EDK. The cordelette was brand new but the static rope was used. I performed two types of tests: a standard EDK end-to-end destructive test and an EDK against an A2 stainless steel Fixe rap ring, which is the same ring used on millions of rap stations. For both tests, I pretensioned all four strands, I tied the EDK with the 6mm on bottom and I tied an overhand backup knot with the 6mm. I used a clove hitch to attach the test sample to a steel carabiner, which was attached to my testing platform.

Testing Layout

Figure one depicts the first test, an end-to-end pull-test.

Figure two shows the second test, which simulates a scenario in which the EDK is only acting as a stopper knot in the belay. In this photo I pulled on the 6mm cordelette, but I also conducted another test in which I pulled on the 11mm. The results were similar for both trials. The backup knot was did not tighten in either of the two tests.

Figure four indicates where the rope failed—at the clove hitch.

Results and Observations

The first test, an end-to-end static pull-test, resulted in the 6mm failing at the hydraulic cylinder with a peak load of 1,187lbf (5.28kN). The EDK knot did not roll; however, <em>the backup overhand knot was quite tight</em>, which implied that the backup knot was loaded. The second test, which simulated the climber using the EDK as a stopper knot against the belay station’s rings, resulted in the knot pulling through the Fixe ring at 800lbf (3.55kN). Worth noting is that I placed a carabiner in the Fixe ring to attach it to my load cell, which restricted the knot’s ability to pull through the ring. In a real-world scenario, the knot would have more room to pull through the ring.

Figure three:

Addendum

I tested the EDK with the 6mm on bottom and with the 6mm on top, both without a backup knot. In both tests, the 6mm broke at the hydraulic cylinder without the knot rolling (although it was close to rolling).

I am imaging myself simul-rapping with a partner, he is on 6 mm and I am on 11 mm static and rope is attached via EDK in to double chain loop on the anchor and bang, there we go , EDK pooped and my partner took 400 footer on the 6mm rope.

I am imaging myself simul-rapping with a partner, he is on 6 mm and I am on 11 mm staticand rope is attached via EDK in to double chain loop on the anchor and bang, there we go , EDK pooped and my partner took 400 footer on the 6mm rope.

Why on earth would you do that?!?

If I absolutely, positively had to use this setup I would use a tandem rappel (i.e. two people on one rap device) with both ropes in the rap device.

I am imaging myself simul-rapping with a partner, he is on 6 mm and I am on 11 mm staticand rope is attached via EDK in to double chain loop on the anchor and bang, there we go , EDK pooped and my partner took 400 footer on the 6mm rope.

Why on earth would you do that?!?

If I absolutely, positively had to use this setup I would use a tandem rappel (i.e. two people on one rap device) with both ropes in the rap device.

well, you can technically rap on 2 mm cord if the other side is 10 mm and main knot is resting solid on the rap ring so testing this EDK knot against 11mm is waste of time .

I could properly use his harbor freight 10 ton press to change the bearing on my vw van.

I am imaging myself simul-rapping with a partner, he is on 6 mm and I am on 11 mm static and rope is attached via EDK in to double chain loop on the anchor and bang, there we go , EDK pooped and my partner took 400 footer on the 6mm rope.

More proof that you never actually climb. No one short of a complete moron would try to simul-rap on 6mm. Go ahead and rap on some 6mm. The EDK wont kill you, but Darwinism surely will.

I am imaging myself simul-rapping with a partner, he is on 6 mm and I am on 11 mm staticand rope is attached via EDK in to double chain loop on the anchor and bang, there we go , EDK pooped and my partner took 400 footer on the 6mm rope.

If I absolutely, positively had to use this setup I would use a tandem rappel (i.e. two people on one rap device) with both ropes in the rap device.

Why would you do that? This setup is extremely common among people that climb reasonably hard (AKA other than Majidoit). I have been using it for years. One person raps both strands, then the other person raps both strands. Kind of like how rapping is supposed to go, pre simul-rap era. One person at a time. None of this hauling ass to the ground with two people on one belay device, or simul-raping on the 6mm crap.

I am imaging myself simul-rapping with a partner, he is on 6 mm and I am on 11 mm static and rope is attached via EDK in to double chain loop on the anchor and bang, there we go , EDK pooped and my partner took 400 footer on the 6mm rope.

More proof that you never actually climb. No one short of a complete moron would try to simul-rap on 6mm. Go ahead and rap on some 6mm. The EDK wont kill you, but Darwinism surely will.

so if no one raps or climb on 6 mm rope then doing a test on EDK serves no purpose unless, a big 900 lbs mama wants to pull the 6 mm rope on double rope rap system and out of his luck, the EDk becomes stuck in some crack and the hand pull forces of the 900 lbs mama causes the rope to break (at EDK) leaving mama on the wall and another job for rescuers .

I am imaging myself simul-rapping with a partner, he is on 6 mm and I am on 11 mm staticand rope is attached via EDK in to double chain loop on the anchor and bang, there we go , EDK pooped and my partner took 400 footer on the 6mm rope.

If I absolutely, positively had to use this setup I would use a tandem rappel (i.e. two people on one rap device) with both ropes in the rap device.

Why would you do that? This setup is extremely common among people that climb reasonably hard (AKA other than Majidoit). I have been using it for years. One person raps both strands, then the other person raps both strands. Kind of like how rapping is supposed to go, pre simul-rap era. One person at a time. None of this hauling ass to the ground with two people on one belay device, or simul-raping on the 6mm crap.

and you would rap with both strand on GG and similar devices ?

nice try

most climbers leave the knot to rest of the anchor ring (generally on the fat rope) and smaller diameter cord is to pull the big rope.

I am imaging myself simul-rapping with a partner, he is on 6 mm and I am on 11 mm static and rope is attached via EDK in to double chain loop on the anchor and bang, there we go , EDK pooped and my partner took 400 footer on the 6mm rope.

Sure, you can imagine this. The real-world data, though, does not support the idea that what you are imagining would actually happen.

I am imaging myself simul-rapping with a partner, he is on 6 mm and I am on 11 mm staticand rope is attached via EDK in to double chain loop on the anchor and bang, there we go , EDK pooped and my partner took 400 footer on the 6mm rope.

If I absolutely, positively had to use this setup I would use a tandem rappel (i.e. two people on one rap device) with both ropes in the rap device.

Why would you do that? This setup is extremely common among people that climb reasonably hard (AKA other than Majidoit). I have been using it for years. One person raps both strands, then the other person raps both strands. Kind of like how rapping is supposed to go, pre simul-rap era. One person at a time. None of this hauling ass to the ground with two people on one belay device, or simul-raping on the 6mm crap.

and you would rap with both strand on GG and similar devices ?

nice try

most climbers leave the knot to rest of the anchor ring (generally on the fat rope) and smaller diameter cord is to pull the big rope.

No Majidoit, most climbers dont use the 6mm as a pull strand, most rap on it. There is no reason not to rap on it. Your posts make it clear you have absolutely no idea what the 6mm is used for in the field. Trying to explain it to you would be like trying to explain how to climb A4 to a gym rat. Not that rapping with a pull strand is hard, but that you are so incredibly inexperienced there is no way I could possibly explain to you in a manner that you would comprehend.